DE 10 2012 105 795 A1 discloses a camshaft having two sliding cam pieces which are accommodated on a main shaft in a rotationally fixed and axially displaceable manner. In order for the sliding cam pieces to be accommodated in a rotationally fixed manner, they have an inner toothing formation, which interacts with an outer longitudinal toothing formation on the main shaft. The two sliding cam pieces have arranged between them an adjustment element which, for the axial displacement of the two sliding cam pieces, can be brought into operative connection with an actuator. The actuator, for this purpose, has guide elements which can engage, by way of a lift movement, in associated lift curves provided on the outside of the adjustment element. Axial displacement of the sliding cam pieces allows various cam tracks of the cam groups to interact with tappet elements, which serve for valve-control purposes in an internal combustion engine. The cam tracks can have different contours, for example it is conceivable for one cam track to be provided for a large valve lift and a further cam track to be provided for a small valve lift or for a zero lift. Depending on the axial position of the sliding cam pieces, it is therefore the case that valve control is operated by way of different valve lifts, but also, or as an alternative, by way of different control periods over the course of camshaft rotation.
The first sliding cam piece shown serves for controlling valves which are assigned to a first cylinder, and the further sliding cam piece serves for controlling valves which are assigned to a second, adjacent cylinder. It is therefore advantageously possible for just one adjustment element in operative connection with just one actuator to activate two sliding cam pieces for controlling the valves of different cylinders.
The disadvantage is that the sliding cam pieces and the adjustment element form a structural unit of considerable length in the center-axis direction of the main shaft. In the case of assembling, the insertion of the camshaft into a module body is therefore possible only by way of bearing bridges which have a split, and therefore open, construction. A module body in the present context is understood to be an accommodating body which is designed, for example, in the form of a hood, of a cover or as some other unit which is arranged on an internal combustion engine and is positioned, in particular, on a cylinder head of an internal combustion engine. The camshaft is set up ready for functioning in said accommodating body.
The definitively made camshaft together with the sliding cam pieces, the adjustment element and possibly also with the main shaft already introduced are thus inserted into the bearing bridges in the module body, and only then are the bearing bridges completed by being assembled with closed bearing passages, and therefore outer bearing shells, which are formed by the bearing bridges, enclose the camshaft over the full circumference only following assembly. It is usually the case here that the sliding cam pieces extend through the bearing bridges and are mounted in the same, and therefore, in addition to a guiding function, the main shaft serves just for introducing the rotary movement into the sliding cam pieces. Closed bearing passages here, within the context of the present invention, are not divided in two, for example formed from two bearing shells which in the installed state supplement one another to form a bearing bore. It is therefore necessary for a shaft, in order to be accommodated in a closed bearing bridge, to be introduced into the bearing bore of the bearing bridge by way of an axial insertion movement. The advantage of a closed bearing bridge here resides, by contrast, in lower production outlay.